Wednesday, March 30, 2016

Declining Trend of Hepatitis A Seroepidemiology in Association with Improved Public Health and Economic Status of Thailand

Hepatitis A virus (HAV) is
transmitted via the fecal-oral route from contaminated food or water. As part
of the most recent survey of viral hepatitis burden in Thailand, we analyzed
the current seroprevalence of HAV in the country and compared with data dating
back to 1971. From March to October, 2014, a total of 4,260 individuals between
one month and 71 years of age from different geographical regions (North = 961;
Central = 1,125; Northeast = 1,109; South = 1,065) were screened for anti-HAV
IgG antibody using an automated chemiluminescent microparticle immunoassay.
Overall, 34.53% (1,471/4,260) possessed anti-HAV IgG antibody, and the
age-standardized seroprevalence was 48.6%. Seroprevalence rates were 27.3%
(North), 30.8% (Central), 33.8% (Northeast) and 45.8% (South) and were markedly
lower than in the past studies especially among younger age groups. The overall
trend showed an increase in the age by which 50% of the population were
anti-HAV IgG antibody: 4.48 years (1971–1972), 6 (1976), 12.49 (1990), 36.02
(2004) and 42.03 (2014).This suggests that Thailand is transitioning from low
to very low HAV endemicity. Lower prevalence of HAV correlated with improved
healthcare system as measured by decreased infant mortality rate and improved
national economy based on increased GDP per capita. The aging HAV immuno-naïve
population may be rendered susceptible to potential HAV outbreaks similar to
those in industrialized countries and may benefit from targeted vaccination of
high-risk groups.

Below: Map of Thailand and the domicile of study participants

Below: Correlation between infant mortality rate (per 1,000 live births), GDP, and age at which 50% of the population possessed anti-HAV antibody